He doesn't know that. He's an idiot. For all he knows, it could be the worst day of his life. 

You know how people say, 'Who knows? I could get hit by a bus tomorrow.' That seems pretty farfetched. 

Until you have a friend who got hit by a bus. 

The point is you never know what kind of day is coming. 

Whenever we think we know the future, even for a second, it changes. Sometimes the future changes quickly and completely. And we're left only with the choice of what to do next.

 We can choose to be afraid of it, to stand there, trembling, not moving, assuming the worst that can happen. 

Or we step forward, into the unknown, and assume it will be brilliant.